From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F0F3C433E9 for ; Mon, 15 Mar 2021 03:38:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3CB7A64E66 for ; Mon, 15 Mar 2021 03:38:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229887AbhCODh5 (ORCPT ); Sun, 14 Mar 2021 23:37:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51998 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229787AbhCODhd (ORCPT ); Sun, 14 Mar 2021 23:37:33 -0400 Received: from mail-io1-xd2b.google.com (mail-io1-xd2b.google.com [IPv6:2607:f8b0:4864:20::d2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A10E0C061574 for ; Sun, 14 Mar 2021 20:37:33 -0700 (PDT) Received: by mail-io1-xd2b.google.com with SMTP id z13so31939309iox.8 for ; Sun, 14 Mar 2021 20:37:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=A6CY6cKc95xTq+TlSR1oRBY2LuTAiSqefWIbt2lRRJM=; b=Ij/PZKQnNuHvmX7UXF1zWmqCCfLzDUCyKJgxu1E5SQJ3RLPSfLQ1L/Jh6HO7JizyOz vSKBD3WJCRIe/4EBhifp2WsofgYnzZ6tbN7eYNyo1G/6xQ6j9aQlVf2imasgWeMUQpf7 vbOdd5jQlpmtZC4n1g03i07MQI8AOrDgRg/EEm5NjS+Pc3794vM/c59a+ca34zz2JBqd chzFANTXdPnr313QcpyizyQ4JzgMMsipzcEisI/qsXS2wQLXFut3SDok8SPToABFjVB7 MiYiSifcRrLXOhsKjAZzQN/NIv5x4iYwa/pJ/twMor/9i00oxvvpLh8hmnR6IWKt1M5U bj5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=A6CY6cKc95xTq+TlSR1oRBY2LuTAiSqefWIbt2lRRJM=; b=hrg9A53cT3jHwovGKMAlq6zL65NWQMm3kuZu8RiNQsO12lIxvyP385A2guTbG14KS1 WPAu3h33iYe9YysxQ/iwxUIahtv1aAlA9pLLT8omvkMRdq5QDwlHW3ZUIxhAaiJqhTGp 9TGV6K4kI39OE1qiYOwVCY4AY8k2UTBNVmfZll3KzzUGTLymdslz5ezPws74lMgFtsTG zuFGnhcFoidrKdc+RD7p7WGrVQ0rBziVelvmrIlUG6yPJ0C0ki/+EJZu8U2figzX3xDW ic+bdFVUPGZYSMH8HyCw2Wycu7jqat+eSl1tAW4M1mZxrTlWKMZWwqdFYM35anoi/Pgd 5gyw== X-Gm-Message-State: AOAM530p1N6BPgNdjtkMGahFg6xmCClhiF2H9DYzzsawCQKTgZxGrZ/j DLjuwTepinvqF9qM1yqYF51WqA== X-Google-Smtp-Source: ABdhPJwKUPdTlbWTs97YHCpuc081aR0MY8JOLfj7riMvasMxJrce3DnhrHVKuVjoIZRdjcJzRK7rIw== X-Received: by 2002:a5d:9f4a:: with SMTP id u10mr6035206iot.186.1615779452941; Sun, 14 Mar 2021 20:37:32 -0700 (PDT) Received: from google.com ([2620:15c:183:200:4d84:eb70:5c32:32b8]) by smtp.gmail.com with ESMTPSA id q207sm6643816iod.6.2021.03.14.20.37.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 14 Mar 2021 20:37:32 -0700 (PDT) Date: Sun, 14 Mar 2021 21:37:27 -0600 From: Yu Zhao To: Andi Kleen Cc: linux-mm@kvack.org, Alex Shi , Andrew Morton , Dave Hansen , Hillf Danton , Johannes Weiner , Joonsoo Kim , Matthew Wilcox , Mel Gorman , Michal Hocko , Roman Gushchin , Vlastimil Babka , Wei Yang , Yang Shi , Ying Huang , linux-kernel@vger.kernel.org, page-reclaim@google.com Subject: Re: [PATCH v1 10/14] mm: multigenerational lru: core Message-ID: References: <20210313075747.3781593-1-yuzhao@google.com> <20210313075747.3781593-11-yuzhao@google.com> <871rchw4x2.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <871rchw4x2.fsf@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 14, 2021 at 07:02:01PM -0700, Andi Kleen wrote: > Yu Zhao writes: Hi Andi! Recovering the context a bit: err = -EBUSY; > > + > > +#ifdef CONFIG_MEMCG > > + if (memcg && atomic_read(&memcg->moving_account)) > > + goto contended; > > +#endif > > + if (!mmap_read_trylock(mm)) > > + goto contended; > > These are essentially spinloops. Surely you need a cpu_relax() somewhere? contended: ... cond_resched(); } while (err == -EAGAIN && !mm_is_oom_victim(mm) && !mm_has_migrated(mm, memcg)); So if it's contended, we break the loop. > In general for all of spinloop like constructs it would be useful to > consider how to teach lockdep about them. > > > + do { > > + old_flags = READ_ONCE(page->flags); > > + new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; > > + VM_BUG_ON_PAGE(new_gen < 0, page); > > + if (new_gen >= 0 && new_gen != old_gen) > > + goto sort; > > + > > + new_gen = (old_gen + 1) % MAX_NR_GENS; > > + new_flags = (old_flags & ~LRU_GEN_MASK) | ((new_gen + 1UL) << LRU_GEN_PGOFF); > > + /* mark page for reclaim if pending writeback */ > > + if (front) > > + new_flags |= BIT(PG_reclaim); > > + } while (cmpxchg(&page->flags, old_flags, new_flags) != > > old_flags); > > I see this cmpxchg flags pattern a lot. Could there be some common code > factoring? Thanks for noticing this. A shorthand macro would be nice. Hmm... let me investigate. I don't know how to do this off the top of my head: A macro can be used like cmpxchg_macro() { func(); } without backslashes and it'll be expanded to do { func(); } while ();